In the following document about python embedding, it is well described how to embed python methods in "C" code. https://docs.python.org/3/extending/embedding.html
I tested the above code, it works well with the GCC g++ compiler as well.
But the above shows examples of calling the global methods not the class methods.
Could anyone show an example about how to create a Python object and call its method from C++?
By doing some investigation, I found that this can be done using the following fourAPIs in series.
PyModule_GetDict ; Gets items belonging to the python module. *
PyDict_GetItemString ; Gets the item corresponding to Python class name.
The following is the sample code that I created even though it still needs to be improved.
// Refer to the following website for more information about embedding the
// Python code in C++.
// https://docs.python.org/2/extending/embedding.html
int main() {
PyObject *module_name, *module, *dict, *python_class, *object;
// Initializes the Python interpreter
Py_Initialize();
module_name = PyString_FromString(
"work.embedding_python_in_cpp.example.adder");
// Load the module object
module = PyImport_Import(module_name);
if (module == nullptr) {
PyErr_Print();
std::cerr << "Fails to import the module.\n";
return 1;
}
Py_DECREF(module_name);
// dict is a borrowed reference.
dict = PyModule_GetDict(module);
if (dict == nullptr) {
PyErr_Print();
std::cerr << "Fails to get the dictionary.\n";
return 1;
}
Py_DECREF(module);
// Builds the name of a callable class
python_class = PyDict_GetItemString(dict, "Adder");
if (python_class == nullptr) {
PyErr_Print();
std::cerr << "Fails to get the Python class.\n";
return 1;
}
Py_DECREF(dict);
// Creates an instance of the class
if (PyCallable_Check(python_class)) {
object = PyObject_CallObject(python_class, nullptr);
Py_DECREF(python_class);
} else {
std::cout << "Cannot instantiate the Python class" << std::endl;
Py_DECREF(python_class);
return 1;
}
int sum = 0;
int x;
for (size_t i = 0; i < 5; i++) {
x = rand() % 100;
sum += x;
PyObject *value = PyObject_CallMethod(object, "add", "(i)", x);
if (value)
Py_DECREF(value);
else
PyErr_Print();
}
PyObject_CallMethod(object, "printSum", nullptr);
std::cout << "the sum via C++ is " << sum << std::endl;
std::getchar();
Py_Finalize();
return (0);
}
